Thin film electroluminescent edge emitter structure with optical lens and multi-color light emission systems

ABSTRACT

A thin film electroluminescent edge emitter structure includes a common electrode layer and control electrodes disposed above the common electrode layer. At least one dielectric layer is disposed between the common electrode layer and control electrodes, and a phosphor layer is interposed between the one dielectric layer and common electrode layer. The common electrode layer, one dielectric layer and the phosphor layer define the light-emitting pixels of the emitter structure. Each pixel has a light-emitting face formed thereon and is operable upon application of electrical excitation to cause the radiation of light energy within its phosphor layer at least in a direction towards the pixel light-emitting face. An optical lens system associated with the pixels includes a preselected contour shaped on the light-emitting face of each pixel to define an optical lens integral therewith to project the light energy passed therethrough in a preselected direction and form a beam of light energy having a preselected beam pattern. A multi-color light emission system employed by the pixels includes a plurality of phosphor zones composing the phosphor layer and capable of projecting different light energy through the light-emitting faces of the pixels. Also, separate edge emitter structures projecting different colors of light can be utilized in a electrophotographic printer.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation-in-part of U.S. Pat. Application Ser.No. 280,909, filed Dec. 7, 1988, now abandoned, which is acontinuation-in-part of U.S. Pat. Application Ser. No. 248,868, filedSept. 23, 1988, now abandoned, and entitled "A Thin FilmElectroluminescent Edge Emitter Structure Having An Integral OpticalLens System".

Reference is hereby made to the following copending applications dealingwith related subject matter and assigned to the assignee of the presentinvention:

1. U.S. Pat. Application Ser. No. 254,282, filed Oct. 6, 1988, now U.S.Pat. No. 4,885,488 and entitled "Process For Defining An Array Of PixelsIn A Thin Film Electroluminescent Edge Emitter Structure".

2. U.S. Pat. Application Ser. No. 273,296, filed Nov. 18, 1988, now U.S.Pat. No. 5,004,956 and "A Thin Film Electroluminescent Edge EmitterStructure On A Silicon Substrate".

3. U.S. Pat. Application Ser. No. 343,697, filed Apr. 24, 1989 now U.S.Pat. No. 4,899,184, and entitled "A Multiplexed Thin FilmElectroluminescent Edge Emitter Structure and Electronic Drive SystemTherefor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a thin film electroluminescent edgeemitter structure, and more particularly, to linearly-arrayedlight-emitting pixels of the thin film edge emitter structureincorporating an optical lens system and a multi-color light emissionsystem.

2. Description of the Prior Art

It is well known that an electroluminescent device may be utilized toprovide an electronically controlled, high resolution light source. Onearrangement which utilizes an electroluminescent device to provide suchlight source is a flat panel display system, such as disclosed in U.S.Pat. No. (4,110,664) to Asars et al and Luo et al U.s. Pat. No.(4,006,383) which are assigned to the assignee of the present invention.However, in a flat panel display system, light emissions providing thelight source are normal to the face of the electroluminescent device andmust pass through one of the electrodes. Thus, the thickness of theelectroluminescent device and the transmissiveness of the electrode arepractical limitations on the brightness of the light emissions which canbe attained by the flat panel display system.

Another arrangement utilizing an electroluminescent device to providesuch light source is a thin film line array, or edge, emitter, such asdisclosed in a U.S. Pat. No. (4,535,341) to Kun et al which is alsoassigned to the assignee of the present invention. The brightness of thelight emissions attained by the thin film electroluminescent edgeemitter structure of the Kun et al patent is not subject to the samelimitations as the flat panel display system due to the fact that itprovides light emissions at the edge of the electroluminescent device.Edge emission come from a depth of the electroluminescent devicecorresponding to its length, and not to its thickness, and does not passthrough one of the electrodes. For reference herein, the length of anelectroluminescent device is the distance between its light emittingedge and its opposite nonlight emitting edge. Thus, edge emissions ofthe thin film line array, or edge, emitter light source are typically 30to 40 times brighter than the face emissions of the flat panel displaylight source under approximately the same excitation conditions.

From the above discussion, it can be appreciated that the thin film edgeemitter structure of the Kun et al patent potentially provides a highresolution light source promising orders of magnitude of improvedperformance over the flat panel face emitter structure in terms of lightemission brightness. However, many areas of thin film edge emitterstructure design are still in need of further improvements to enhanceperformance overall. Two such areas are the pattern and levels of lightenergy projected by the edge emitter structure.

SUMMARY OF THE INVENTION

The present invention provides a thin film edge emitter structuredesigned to satisfy the aforementioned needs. The edge emitter structureof the present invention has linearly-arrayed light-emitting pixelswhich employ novel features relating to the pattern and levels of lightenergy projected by pixels of the edge emitter structure. Moreparticularly, the novel features relate to an optical lens system and amulti-color light emission system incorporated in the light-emittingpixels. While these novel features are adapted for working together tofacilitate further improvements in the overall performance of the thinfilm edge emitter structure, it is readily apparent that such featuresmay be incorporated either singly or together in such structure.

Accordingly, the present invention is set forth in a thin filmelectroluminescent edge emitter structure which preferably includes acommon electrode layer, a plurality of control electrodes spacedtherefrom, at least one dielectric layer interposed between the commonelectrode layer and the plurality of control electrodes, and alight-energy generating material in the form of a phosphor layerinterposed between the one dielectric layer and the control electrodesand having a light-emitting edge face extending in a direction betweenthe one dielectric layer and control electrodes. Another dielectriclayer can be interposed between the common electrode layer and thephosphor layer.

The common electrode layer, the phosphor layer, the one dielectric layerand the control electrodes form a generally stacked laminar arrangementand are disposed on a layer of substrate material. In addition to theedge face of the phosphor layer, the common electrode layer, the onedielectric layer, and the plurality of control electrodes haverespective edge faces aligned with one another and with thelight-emitting edge face of the phosphor layer. The common electrodelayer, the phosphor layer, the one dielectric layer, and the pluralityof control electrodes define a plurality of pixels each having alight-emitting edge face. The plurality of control electrodes and thecommon electrode layer are adapted to be connected with an excitationdevice for applying an excitation signal to selected pixels. Theapplication of an excitation signal to a selected pixel causes thephosphor layer associated with the pixel to radiate light energy in atleast a direction towards its light-emitting face.

One novel feature of the present invention is an optical lens systemassociated with the edge emitter structure. Preferably, thelight-emitting edge face of each pixel is shaped to a preselectedcontour to define an optical lens integral with the pixel to refract thelight energy passing therethrough. Depending upon the specific contourof the integral optical lens, the refracted light energy is projected ina preselected direction and formed into a beam of light energy having apreselected beam pattern.

Another novel feature of the present invention is a multi-color lightemission system associated with the edge emitter structure. The phosphorlayer is divided into a plurality of phosphor zones each formed from apreselected composition of light-radiating materials. Each of thecontrol electrodes are disposed on the one dielectric layer in alignmentwith one phosphor zone. The color of the radiated light energy isdependent upon the composition of the light-radiating materials in thephosphor zone.

Still another novel feature of the present invention relates toprovision of an electrophotographic printer which utilizes arrays ofseparate thin film electroluminescent edge emitters projecting differentcolors of light. In one embodiment, separate edge emitters projectinglight are positioned with sets of electrophotographic components about aphotoreceptor drum. In another embodiment, separate edge emitters arearrayed to project different colors of light in radial convergentrelationship through a lens for focussing the light of each emitter on aphotoreceptor drum. In yet another embodiment, separate edge emitterswhich each project white light are arrayed with differentcolor-sensitive filters for projecting different colors of light onto amulti-color sensitive paper. In still another embodiment, separate edgeemitters projecting light are positioned with sets ofelectrophotographic components serially arranged along a photoreceptorbelt.

The novel features of the present invention can be used together toprovide an optical lens system with the pixels and to project and passthe colored light energies from the respective phosphor zones of thepixels through the optical lens system and into an overlappingrelationship for different photoreceptive applications. Further, thecolored light energies projected by the respective pixels into theoverlapping relationship are blended at the areas of overlap to form aresultant light image having a color dependent upon the colors of thelight energies projected by the pixels.

These and other features and advantages of the present invention willbecome apparent to those skilled in the art upon a reading of thefollowing detailed description when taken in conjunction with thedrawings wherein there is shown and described illustrative embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the following detailed description, reference will bemade to the attached drawings in which:

FIG. 1 is a perspective view of a thin film electroluminescent edgeemitter structure having a channel formed therein to define a pair ofindividual light-emitting pixels.

FIG. 2 is a fragmentary top plan view of a forward portion of the edgeemitter structure of FIG. 1, illustrating the extremities of the beamformed as the structure is operated to project light energy.

FIG. 3 is a perspective view of one embodiment of the thin filmelectroluminescent edge emitter structure of the present invention,illustrating the light-emitting face of each pixel in the structureshaped to a preselected contour to form an optical lens integral withthe pixel.

FIG. 4 is a fragmentary top plan view of a forward portion of the thinfilm edge emitter structure of FIG. 3, illustrating the beams formed bythe light energy-projecting lens integral with each pixel as thestructure is operated to project light energy.

FIG. 5 is a view similar to FIG. 4, illustrating the contour of analternate embodiment of the light energy-projecting lens integral witheach pixel.

FIG. 6 is a view similar to FIG. 4, illustrating the contour of anotheralternate embodiment of the light energy-projecting lens integral witheach pixel.

FIG. 7 is a view similar to FIG. 4, illustrating the contour of stillanother alternate embodiment of the light energy-projecting lensintegral with each pixel.

FIG. 8 is a perspective view similar to FIG. 3 of an alternateembodiment of the thin film electroluminescent edge emitter structure ofthe present invention, illustrating a pair of adjacent pixels eachhaving a serrated light-emitting face.

FIG. 9 is a top plan view of a forward portion of one of the pixels ofFIG. 8, illustrating a waveguide effect on light energy passed throughthe serrated light-emitting face of the pixel.

FIG. 10 is a top plan view of a forward portion of three light-emittingpixels positioned in side-by-side relationship, each pixel having alight-emitting face shaped to a preselected contour to project lightenergy passed therethrough into an overlapping relationship with thelight energy projected by the other pixels.

FIG. 11 is a front elevational view of one embodiment of a multi-colorarray of thin film electroluminescent edge emitters of the presentinvention.

FIG. 12 is a fragmentary top plan view of the multi-color edge emitterarray of FIG. 11.

FIG. 13 is a front elevational view of another embodiment of amulti-color edge emitter array of the present invention.

FIG. 14 is a schematic representation of three separate edge emittersprojecting light and arrayed with sets of electrophotographic componentsabout a photoreceptor drum.

FIG. 15 is a schematic representation of three separate edge emittersarrayed to project different colors of light in radial convergentrelationship and aligned with a lens for focussing the light of eachemitter on a photoreceptor drum.

FIG. 16 is a schematic representation of three separate edge emittersarrayed to project white light through three different color-sensitivefilters onto a multi-color sensitive paper.

FIG. 17 is a schematic representation of three separate edge emittersand sets of electrophotographic components serially arranged along aphotoreceptor belt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In General

Referring to the drawings, and particularly to FIGS. 1 and 2, there isillustrated an example of an edge emitter structure, such as a thin filmelectroluminescent (TFEL) edge emitter structure, generally designatedby the numeral 10, which may be utilized as a solid state,electronically controlled high resolution light source. Both theconstruction and operation of this TFEL edge emitter structure aredisclosed in the first U.S. patent application cross-reference abovewhich is assigned to the assignee of the present invention.

Referring first to FIG. 1, the TFEL edge emitter structure 10 preferablyincludes a common electrode layer 12, a first dielectric layer 14, asecond dielectric layer 16, a light-energy generating material in theform of a phosphor layer 18, and a plurality (only a pair being shown)of excitation or control electrodes 20. The common electrode layer 12 isdisposed on a layer of substrate material 22. The first dielectric layer14 is disposed on the common electrode layer 12, and the seconddielectric layer 16 is spaced from the first dielectric layer 14. Thephosphor layer 18 is interposed between first and second dielectriclayers 14, 16, and the pair of control electrodes 20 are disposed on thesecond dielectric layer 16.

It should be understood that although the TFEL edge emitter structure 10illustrated in FIG. 1 includes first and second dielectric layers 14,16, one or the other of the first and second dielectric layers may beeliminated from the structure if desired. If the first dielectric layer14 is not included in the TFEL edge emitter structure 10, then it isapparent that the phosphor layer 18 will be interposed between thecommon electrode layer 12 and the second dielectric layer 16.Alternatively, if the second dielectric layer 16 is not included in theTFEL edge emitter structure 10, then it is apparent that the phosphorlayer 18 will be interposed between the first dielectric layer 14 andthe control electrodes 20. Whether the TFEL edge emitter structure 10has one or two dielectric layers, it operates identically as illustratedand described below with reference to the two dielectric layers 14, 16.It should be understood that the TFEL edge emitter structuresillustrated in the other figures may also be formed to include only asingle dielectric layer as in the case of the structure 10.

In addition, it should be understood that although first and seconddielectric layers 14, 16 are illustrated in FIG. 1 as unitary layers,each dielectric layer may in fact consist of a plurality of sublayers.The sublayers may be formed from different dielectric materials, andthose skilled in the art may select the sublayer material utilizeddepending upon the dielectric properties desired.

The common electrode layer 12, first and second dielectric layers 14,16, phosphor layer 18, and the pair of control electrodes 20 of the TFELedge emitter structure 10 form a pair of light-emitting pixels 24 inwhich the common electrode layer 12 and the first and second dielectriclayers 14, 16 with phosphor layer 18 interposed therebetween are commonto both pixels 24. As also seen in FIG. 1, a generally rectangularchannel 26 is formed in the TFEL edge emitter structure 10 and extendsfrom the top surface 16A of the second dielectric layer 16 downwardthrough the various layers 16, 18, 14, 12 to the top surface 22A of thesubstrate layer 22. The channel 26 also extends a preselected distancerearwardly from a front or outer edge face 24A of each pixels 24 intothe central portion of the TFEL edge emitter structure 10. Oppositelateral sides and an inner end of the channel 26 form opposing lateraledge faces 24B of the adjacent pixels 24 and an inner edge face 24Cwhich extends between and interconnects the opposing lateral edge faces24B. The channel 26 serves to optically isolate adjacent pixels 24 fromone another to prevent optical cross-talk.

Thus, the pair of control electrodes 20 define, in combination with theremaining components of the TFEL edge emitter structure 10, the pair ofpixels 24 as illustrated in FIG. 1. Although only a pair of adjacentpixels 24 and one channel 26 are illustrated in FIG. 1, it should beunderstood that the actual number of pixels 24 and channels 26 which maybe formed in a TFEL structure such as TFEL structure 10 will bedependent upon the structure's overall length and the total number ofcontrol electrodes 20 actually formed in the layer of control electrodematerial.

The control electrode 20 of each light-emitting pixel 24 and electrodelayer 22 common to the pair of pixels are connected with an electricalexcitation source 28. As known in the art, each excitation source 28 isin electrical communication with common electrode layer 12 and one ofthe pair of control electrodes 20 to provide the excitation signalnecessary to excite the electroluminescent phosphor layer 18 common tothe pair of pixels 24. Upon the application of an excitation signal toan individual pixel 24, via the one control electrode 20 and the commonelectrode layer 12, the portion of the phosphor layer 18 associated withthe individual pixel radiates light energy which is projected throughthe light-emitting front edge face 24A of the pixel.

Thus, the front edge faces 24A of the pixels 24 of the TFEL edge emitterstructure 10 are the light emission sources of the structure. A rearedge face 24D of each pixel 54 is coated with a layer of non-metallicreflective coating 30. The layer of reflective coating 30 is operable toreflect a great portion of the light present at the rear edge face 24Dof an individual pixel 24 in a general direction towards the oppositelight-emitting edge face 24A of the pixel.

The pixels 24 of the TFEL edge emitter structure 10 illustrated in FIGS.1 and 2 have light-emitting faces 24A of planar configuration. Thus, thelight energy radiated within phosphor layer 18 of each pixel 24 upon theapplication of an excitation signal across electrodes 12, 20 isrefracted at the planar light-emitting face 24A and projected in anaturally diverging beam pattern to form a constantly expanding beam oflight energy whose boundaries are designated by the letters A in FIG. 2.Stated in another manner, since the phosphor layer 18 has a higher indexof refraction than the medium adjacent to light-emitting face 24 (i.e.air), and each light-emitting face 24A is planar in configuration, thelight energy generated within the phosphor layer 18 of each pixel 24 isrefracted at planar light-emitting face thereof 24A and projectedthrough the air medium to form a beam pattern which diverges naturallyin a direction Y parallel with the width of the pixel 24. The use of theTFEL edge emitter structure 10 having planar light-emitting pixel faces24A as a high resolution light source may not be desired in applicationswhich require the high resolution light source to project light energyin a preselected direction and form a beam of light energy having atightly controlled converging, collimated or diverging beam pattern.

TFEL Edge Emitter With Optical Lens System

Referring to FIG. 3, there is illustrated a TFEL edge emitter structure32 having a plurality of light-emitting pixels 34 now adapted to projectradiated light energy in a desired direction and form a beam of lightenergy having a preselected, tightly controlled beam pattern. The pixels34 have an optical lens system, generally designated 36, associated withtheir light-emitting front edge faces 34A in accordance with one novelfeature of the present invention. In view that the only differencebetween the TFEL edge emitter structures 10 (FIG. 1) and 32 (FIG. 3)relate to the configurations of their respective light-emitting edgefaces 24A and 34A, the same reference numerals are used to identifycomponents of the edge emitter structure 32 of FIG. 3 that are identicalto corresponding components of the structure 10 of FIG. 1 as justdescribed above.

As seen in FIG. 3, the optical lens system 36 is defined by preselectedcontours shaped or configured on the light-emitting edge faces 34A ofthe respective pixels 34. In effect, the contours define optical lensintegral with the pixels 34. In contrast to the planar configuration ofthe light-emitting edge faces 24A of the pixels 24, the contours 34shaped on the light-emitting edge faces 24A of the respective pixels 24function to permit projecting of light energy passed through thecontoured faces 34A in the desired preselected direction and formed inthe desired preselected beam pattern. For example, the light-emittingedge face 34A of each pixel 34 illustrated in FIG. 3 is shaped to aconvex contour viewed from the front of the pixel. As in the case of thepixels 24 of FIG. 1, the front light-emitting face 34A of each pixel 34is formed by the front edge faces of the first and second dielectriclayers 14, 16, the common and control electrodes 12, 20, and thephosphor layer 18; however, now all of the front edge faces of thesesame components are configured in the desired preselected contour.

In the same manner as previously described, the application of anelectrical excitation signal delivered from excitation source 28 to thephosphor layer 18 of each pixel 34 causes the phosphor layer associatedwith each pixel to radiate light energy. The light energy radiatedwithin the phosphor layer 18 associated with an individual pixel 34passes through the phosphor layer in a direction towards the individualpixel light-emitting edge face 34A. Since the index of refraction ofphosphor is approximately 2.4, and the index of refraction of the mediumexternal to light-emitting face 34A is, for example, 1.0 for an airmedium, it is seen that light energy passing from the interior of anindividual pixel phosphor layer 18 to the external medium surroundingthe pixel will be refracted at pixel light-emitting face 34A. However,now the preselected contour of the face 34A will tightly control thedirection and beam pattern of the light refracted at the face. Byvarying the contour of an individual pixel light-emitting face 34A, thelight energy refracted at the light-emitting face may be projected in adesired direction and shaped into a beam of light energy having apreselected beam pattern.

In addition, the light-emitting face 34A of each pixel 34, andparticularly the edge face of each pixel phosphor layer 18, issubstantially perpendicular to the phosphor layer itself and also to thecommon electrode layer 12 and control electrode 20. As a result, thelight energy refracted by each pixel integral lens will be oriented in adirection parallel with the width Y of the pair of pixels 34.

Now referring to FIGS. 4 through 7, there are illustrated exemplaryembodiments of other preselected contours forming the lightenergy-projecting lens integral with each of the pixels 34. The lengthand origin of the radius R, which determines the radius of curvature ofthe integral optical lens defined by the respective contour oflight-emitting edge face 34A, may be varied depending upon whether it isdesired to project a beam of light energy having a converging, divergingor collimated beam pattern. Thus, by controlling the length and originof radius R, the light energy beam pattern may be correspondinglycontrolled. This allows the beam pattern to be shaped for a specificapplication.

As seen in FIG. 5, varying the radius of curvature of each pixellight-emitting face 34A between R' and R" results in a correspondingchange in the contour of each light-emitting face. Thus, by selecting adesired radius of curvature for the concave light-emitting face 34A ofeach pixel 34, the light energy projected at the light-emitting face mayhave a converging beam pattern with a controlled rate of convergence, adiverging beam pattern with a controlled rate of divergence, or acollimated beam pattern. As previously described with reference to FIG.3, since the light energy refracted at light-emitting face 34A travelsin a direction substantially perpendicular to light-emitting face, theconverging, diverging or collimated beam of light energy is orientedparallel to the width Y of the pair of pixels.

FIG. 6 illustrates an outwardly expanding conical end portion 34B oneach pixel 34 bounded by a pair of side faces 34C positioned indivergent relationship with each other. The light-emitting front face34A which forms the integral optical lens extends between andinterconnects the side edge faces 34C at their front edges. Eachlight-emitting face 34A has a convex contour viewed from the front ofthe pixel 34. As previously described, the radius of curvature of eachconvex light-emitting face 34A may be varied as required to projectlight energy in a desired direction and form a beam of light energyhaving either a converging, diverging or collimated beam pattern.

FIG. 7 illustrates pixels 34 each having an integral optical lens on itsfront light-emitting face 34A defined by a contour of different shapedcurvature. Specifically, each light-emitting face 34A has a concavecontour viewed from the front of the pixel 34. The origin of the radiusR is located forward of the pixel. The integral optical lens defined bythe concave contour is operable to project a beam of light energy havinga diverging beam pattern, as represented by the arrows. As with theconvex light-emitting faces illustrated in FIGS. 3 through 6, the radiusof curvature R of each concave light-emitting face 34A in FIG. 7 may bevaried to produce a projected beam of light energy having a divergingbeam pattern and a controlled rate of divergence.

Now referring to FIG. 8, there is illustrated an alternate embodiment ofa TFEL edge emitter structure, generally designated 38. Except for thedifference to be described below, TFEL- edge emitter structure 38 has aconstruction generally the same as the TFEL edge emitter structure 10 ofFIG. 1, and the components thereof identical to corresponding componentsof the structure 10 are identified with the same reference numerals. Asseen in FIG. 8 and particularly in FIG. 9, the difference is that thelight-emitting edge face 40A of each pixel 40 has a generally serratedcontour. Specifically, the light-emitting face 40A is formed by aplurality of rectangular protuberances 42 separated from each other by aplurality of recesses 44. As with the light-emitting faces 34A of thepixels 34 described in FIGS. 3 through 7, the light-emitting face 40A ofeach pixel 40 defines an optical lens integral with the pixel to projectthe light energy passed therethrough in a preselected direction and forma beam of light energy having a preselected light pattern. Since theoptical lens formed by light-emitting face 40A has a serrated contour,as can be realized from FIG. 9 the plurality of protuberances 42 formingthe serration act as waveguides to control the rate of divergence of thelight energy projected by the pixel.

TFEL Edge Emitter With Multi-Color Light Emission System

Referring now to FIG. 10, in accordance with another novel feature ofthe present invention, a multi-color light emission system is associatedwith a TFEL edge emitter structure, generally designated 46. The TFELedge emitter structure 46 has a plurality of light-emitting pixels 48,for example, three such pixels 48 positioned in side-by-siderelationship on the substrate layer 22. Each pixel 48 illustrated inFIG. 10 has the same layered configuration and components as the pixels24 and 34 illustrated in FIGS. 1 through 9 and described in detailearlier with reference to the pixels 24 of FIG. 1.

Further, the pixels 48 of the TFEL edge emitter structure 46 employs theoptical lens system in accordance with one novel feature of the presentinvention described above. Before describing the multi-color lightemission system associated with the structure 46, the optical lenssystem of the structure 46 will be briefly described.

Each pixel 48 has an integral, lens-defining light-emitting face 48Ashaped to a concave contour viewed from the front of the pixel. Byangularly spacing the concave, light-emitting front edge faces 48A ofthe pair of outer pixels 48 by a preselected angle C from dotted lines Lwhich are perpendicular to the longitudinal directions of the pixels,the beams of light energy projected by the outer pixels 48 are projectedinto overlapping relationship with the beam of light energy projected bythe center pixel 48. Thus, the three pixels 48 positioned inside-by-side relationship project three beams of light energy intooverlapping relationship at a plane P. The three beams of light energyare blended at the area of the overlap to form a resultant linear lightimage at plane P extending between the points of coincident of thearrows in FIG. 10 on the plane 10.

In accordance with the second novel feature of the present invention,the multi-color light emission system is provided in the light-radiatingphosphor layer of each pixel 48. The phosphor layer of the TFEL edgeemitter structure 46 is divided into a plurality of phosphor zones eachformed from a different preselected composition of light-radiatingmaterials. Each different phosphor zone is associated with a differentone of the pixels 48 in FIG. 10. The control electrode of each pixel isdisposed in alignment with the one phosphor zone of the pixel. Thus,radiation of the particular light energy color of an individual pixel 48can be controlled by excitation of its control electrode. Therefore, byselecting the specific compositions of light-radiating materials in thephosphor zones within the pixels, the desired spectrum of light energycolors radiated by the pixel can be established.

If, for example, the phosphor layer has a first zone associated with thepixel 48(1) of a first preselected composition of light-radiatingmaterials, a second zone associated with the pixel 48(2) of a secondcomposition of light-radiating materials, and a third zone associatedwith the pixel 48(3) of a third preselected composition oflight-radiating materials, then three beams of light energy at first,second and third preselected colors will be projected into overlappingrelationship at the plane P. The contours defining the lenses on thelight-emitting edge faces 48A of the pixels 48 cause blending of thethree colored beams of light energy at the area of the overlap to form alinear light image having a resultant color dependent on the colors ofthe first, second and third beams of light energy. The plane P can be agiven location on a photoreceptor or a photosensitive paper.

Thus, if the first zone is a red phosphor (ZnS:Sm), the second zone is agreen phosphor (ZnS:Tb) and the third zone is a blue phosphor (SrS:Ce),it is seen that the linear image formed at plane P will have a resultantcolor which is a blend of the colors, red, green and blue. Further, byvarying the frequency of the excitation signal across the control andcommon electrode of one or more pixels, the colored light energyradiated by the phosphor zone(s) associated with the pixel(s) may bevaried in intensity. Thus, the individual beam(s) of light energyprojected will also vary in intensity. It can be seen that by varyingthe intensity of a preselected combination of beams of light energyprojected into overlapping relationship, a resultant light image may beformed having a desired color.

If desired, the trio of different colored light-emitting pixels48(1)-48(3) can be arrayed differently than the side-by-side arrangementof FIG. 10. FIGS. 11 and 13 illustrate an arrangement of the pixels 48in stacked arrays. In FIGS. 11 and 12, two of the pixels 48(1) and 48(2)are disposed on top of the third pixel 48(3) of the trio. In FIG. 13, aplurality of pixel stacks are illustrated with each stack being composedof the three pixels 48(1)-48(3) placed one on top of the other.

Multi-Color Arrays of Edge Emitter Structures

In accordance with a third novel feature of the present invention, themulti-color emission system is formed by an array of separate TFEL edgeemitter structures 50 projecting light for forming a multi-color imagepattern. If desired, the emitter structures 50 can employ the opticallens system described earlier.

FIG. 14 depicts schematically an electrophotographic printer 52 having aphotoreceptor 54 in the form of a drum and a plurality of sets ofelectrophotographic components, each of which is conventional per se.The sets of components are serially arranged about the drum 54. Thecomponents of each set, also in a serial arrangement along the drum 54,are a cleaner 56, an electrical charge device 58 (such as a coronawire), and a toner 60. Each toner 60 is of a different color, such asred, green and blue. One of the three separate edge emitter structures50 is disposed within each set between the charge device 58 and thetoner 60. Each edge emitter structure 50 projects monochromatic light,exposing three separate sections of the photoreceptor drum 54. Each ofthe three photoreceptor sections is sensitized to one of the threecolors, accepts the different color toners and prints a page insequence, resulting in a full color page S after three cycles. Fuserrolls 62 are provided downstream of the photoreceptor drum 54 forcompleting the electrophotographic process.

FIG. 15 shows schematically another arrangement of separate TFEL edgeemitter structures 50 arrayed to project different colors of light forforming a multi-color image pattern on the photoreceptor drum 54. Inthis arrangement, a lens 64 separate from the edge emitter structures 50is provided between the light-emitting faces of the structures 50 andthe drum 54 for focussing light on the drum 54. The different coloredlight-emitting edge emitter structures 50 are disposed to project thedifferent colors of light in a radial convergent relationship throughthe lens 64 to the drum 54.

FIG. 16 is a schematic representation of three identical TFEL edgeemitter structures 66 which each projects the same white light. In thisarrangement, different filters 68 having different color sensitivitiesare used to obtain the different colors form the white light. The whitelight from the three edge emitter structures 66 is thus projectedthrough the three different color-sensitive filters 68 onto themulti-color sensitive medium 70 for forming a multi-color image patternon the medium. One example of the medium 70 is color-sensitive papermarketed under the trademark Cycolor by Mead Imaging of Miamisburg,Ohio. In the case where blue color is not required, three colors can beobtained from a commonly used broad band manganese emission. Threenarrow bandpass filters 68 for producing green, yellow and red colorswould be used.

And FIG. 17 shows another electrophotographic printer 72 which is amodification of the printer 52 seen in FIG. 14. The modified printer 72has the same basic sets of components 56-60 as the printer 52 and so areidentified with the same reference numerals. However, instead of thesets of components being arrayed serially about a photoreceptor drum 54,as in printer 52, they are now arranged along a photoreceptor belt 74which is entrained about a series of rollers 76. Also, now there is aseparate fuser 78 associated with each set of components and a driveroll 80 is disposed on an opposite side of each fuser 78 for conveyingthe paper S.

It is thought that the present invention and many of its attendantadvantages will be understood from the foregoing description and it willbe apparent that various changes may be made in the form, constructionand arrangement of the parts of the invention described herein withoutdeparting from the spirit and scope of the invention or sacrificing allof its material advantages, the forms hereinbefore described beingmerely preferred or exemplary embodiments thereof.

We claim:
 1. In an edge emitter structure which includes a plurality ofpixels, each pixel having light-energy generating material and alight-emitting edge face, said light-energy generating material uponelectrical excitation being operable for radiating light energy throughsaid light-emitting edge faces of said pixels, an optical lens systemcomprising:a preselected contour shaped on said light-emitting edge faceof each pixel to define an optical lens integral with said pixel facefor refracting said light energy passing therefrom so as to project saidlight energy in a preselected direction and thereby form said lightenergy into a beam having a preselected beam pattern; said light-energygenerating material being a phosphor material.
 2. The edge emitterstructure as recited in claim 1, wherein said preselected contour ofsaid light-emitting face of each pixel has a predetermined curvature forrefracting said light energy to form a beam of light energy having aconverging beam pattern.
 3. The edge emitter structure as recited inclaim 1, wherein said preselected contour of said light-emitting face ofeach pixel has a predetermined curvature for refracting said lightenergy to form a beam of light energy having a collimated beam pattern.4. The edge emitter structure as recited in claim 1, wherein saidpreselected contour of said light-emitting face of each pixel has apredetermined curvature for refracting said light energy to form a beamof light energy having a diverging beam pattern.
 5. In a thin filmelectroluminescent edge emitter structure which includes a commonelectrode layer, a plurality of control electrodes spaced therefrom, atleast one dielectric layer interposed between said common electrodelayer and said control electrodes, and a phosphor layer interposedbetween said one dielectric layer and said control electrodes saidcommon electrode layer, phosphor layer, one dielectric layer and controlelectrodes having respective edge faces aligned with one another anddefining a plurality of pixels each having a light-emitting edge face,said phosphor layer upon electrical excitation being operable forradiating light energy through said light-emitting edge faces of saidpixels, an optical lens system comprising:a preselected contour shapedon said light-emitting edge face of each pixel to define an optical lensintegral with said pixel face for refracting said light energy passingtherefrom so as to project said light energy in a preselected directionsaid light energy into a beam having a preselected beam pattern.
 6. Theedge emitter structure as recited in claim 5, wherein:said commonelectrode layer and said control electrode of each pixel extend insubstantially parallel planes; and said light-emitting face of eachpixel is substantially perpendicular to said planes of said common andcontrol electrodes.
 7. The edge emitter structure as recited in claim 6,wherein said light-emitting face of each pixel is positioned relative tosaid planes of said common and control electrodes such that said beam oflight energy projected from said face is oriented in a planesubstantially parallel therewith.
 8. The edge emitter structure asrecited in claim 5, said preselected contour of said light-emitting faceof each pixel has a predetermined curvature for refracting said lightenergy to form a beam of light energy having a converging beam pattern.9. The edge emitter structure as recited in claim 8, wherein saidpredetermined curvature of said light-emitting face contour is convex asviewed from the front of said pixel face.
 10. The edge emitter structureas recited in claim 5, wherein said preselected contour of saidlight-emitting face of each pixel has a predetermined curvature forrefracting said light energy to form a beam of light energy having acollimated beam pattern.
 11. The edge emitter structure as recited inclaim 10, wherein said predetermined curvature of said light-emittingface contour is convex as viewed from the front of said pixel face. 12.The edge emitter structure as recited in claim 5, wherein saidpreselected contour of said light-emitting face of each pixel has apredetermined curvature for refracting said light energy to form a beamof light energy having a diverging beam pattern.
 13. The edge emitterstructure as recited in claim 12, wherein said predetermined curvatureof said light-emitting face contour is concave as viewed from the frontof said pixel face.
 14. The edge emitter structure as recited in claim5, wherein said preselected contour of said light-emitting face of eachpixel is generally serrated for refracting said light energy to form abeam of light energy having a diverging beam pattern.
 15. The edgeemitter structure as recited in claim 5, wherein one of said electrodesis disposed on a layer of substrate material.
 16. The edge emitterstructure as recited in claim 5, wherein another dielectric layer isinterposed between said common electrode layer and said phosphor layer.17. In a thin film electroluminescent edge emitter structure whichincludes a common electrode layer, a plurality of control electrodesspaced therefrom, at least one dielectric layer interposed between saidcommon electrode layer and said control electrodes, and a phosphor layerinterposed between said one dielectric layer and said controlelectrodes, said common electrode layer, phosphor layer, one dielectriclayer and control electrodes having respective edge faces aligned withone another and defining a plurality of pixels each having alight-emitting edge face, said phosphor layer upon electrical excitationbeing operable for radiating light energy through said light-emittingedge faces of said pixels, a multi-color light emission systemcomprising:a plurality of phosphor zones composing said phosphor layer,said zones being formed from different preselected compositions oflight-radiating materials for passing light of different colors throughsaid light-emitting edge faces of said pixels; said light-emitting faceof each pixel being shaped to a preselected contour to define an opticallens integral with said pixel face for refracting said color lightenergy passing therefrom so as to project said colored light energy intoan overlapping relationship with the colored light energy refracted andprojected by other of said pixels.
 18. The edge emitter structure asrecited in claim 17, wherein each of said control electrodes disposed onsaid one dielectric layer is in alignment with one of said phosphorzones.
 19. The edge emitter structure as recited in claim 17, whereinsaid colored light energy projected by said pixels into said overlappingrelationship is blended at the area of said overlap to form a resultantlight image having a color dependent upon the color of said light energyprojected by each of said pixels.
 20. The edge emitter structure asrecited in claim 17, wherein:said phosphor zones includes a first zoneformed from a first preselected composition of light-radiatingmaterials, a second zone formed from a second preselected composition oflight-radiating materials and a third zone formed from a thirdpreselected composition of light-radiating materials; said first, secondand third phosphor zones are associated with first, second and thirdpixels, respectively; and said light-emitting face of each of saidfirst, second and third pixels is shaped to a preselected contour toproject light energy at a first, second and third preselected color intoan overlapping relationship for blending at the area of said overlap toform a linear light image having a resultant color determined by saidfirst, second and third preselected colors.
 21. The edge emitterstructure as recited in claim 20, in which:said first, second and thirdcolors are selected from a group consisting of the colors, red, blue andgreen.
 22. The edge emitter structure as recited in claim 17, furthercomprising:means for varying the frequency of electrical excitationapplied to selected ones of said plurality of pixels for varying theintensity of said colored light energy radiated by said selected ones ofsaid pixels.
 23. The edge emitter structure as recited in claim 17,wherein another dielectric layer is interposed between said commonelectrode layer and said phosphor layer.
 24. The edge emitter structureas recited in claim 17, wherein said light-emitting edge face each ofsaid pixels has a convex contour as viewed from the front of said pixelface to define an integral, convex optical lens.